1. Field of the Invention and Related Art Statement
This invention relates to a signal processor which processes signals obtained from an endoscope and which is capable of changing and optimizing outline enhancement frequencies for enhancement of an image outline of an object depending upon the type of the object.
In recent years, endoscopes are increasingly used with an elongated insertion portion capable of being inserted into a body cavity in order to diagnose a symptom of an affected part therein without dissecting any body part and to perform, if necessary, a treatment using desired instruments.
In a system which makes use of a type of endoscope using an image guide, it is difficult to record or reproduce an image obtained by the endoscope. Therefore, endoscopes designed to produce video signals in order to facilitate recording and reproduction of images have been proposed. The following are two types of devices for generating of video signals from an endoscope:
(a) an electronic endoscope which has a solid-state image pickup device disposed in its head portion, wherein video signals are formed from outputs from the image pickup device; and
(b) an external endoscope camera which is detachably attached to an ocular portion of a fiber scope for observation which is formed of a bundle of fibers extending from the head to an ocular section of the endoscope, wherein video signals are formed from signals output from the camera.
Outline enhancement can be effected by these systems in such a manner that, as disclosed in Japanese patent application No. 181630/1986, video signals including R (red), G (green) and B (blue) signals and luminance signals are formed from signals obtained by image pickup from an object; and outline enhancement processing is performed with respect to each image signal in the same frequency range predetermined and set in the circuit. The frequency range that defines the range of enhancement cannot be changed.
Examples of objects which can be observed by an endoscope and which need to be observed specially in detail are various lesion portions, vessels, and so forth. The frequency range in which image signals are formed for the image of such a portion covers several MHz.
Accordingly, frequencies which characterize and observed portion differ depending upon the type of the portion, and it is not always possible to obtain optimum outline enhancement effects and, hence, suitable diagnostic performance for an observed portion if a system for observation is used in which the setting of the enhancement frequency range is constant and cannot be changed.